The document discusses using Scala for Android development instead of Java. It provides information on Scala and why it is a good fit for Android. Key points include: - Scala is a functional, object-oriented, statically typed programming language that runs on the JVM and DalvikVM, making it suitable for Android. - Code examples show how Scala allows for lazily loading views, implicit conversions, and implicit context injection, reducing boilerplate compared to Java. - The shadowsocks Android project is presented as a sample of building an Android app in Scala, including its structure, use of SBT build tool, and best practices.

1. Android Development
Without Java

2. Android Development
With Scala

3. Scala

4. Scala is

5. Scala is
A Functional

6. Scala is
A Functional
Object Oriented

7. Scala is
A Functional
Object Oriented
Statically Typed

8. Scala is
A Functional
Object Oriented
Statically Typed
Scalable

9. Scala is
A Functional
Object Oriented
Statically Typed
Scalable
Language

10. Scala is
A Functional
Object Oriented
Statically Typed
Scalable
Language
Running on JVM

11. Scala is
A Functional
Object Oriented
Statically Typed
Scalable
Language
Running on JVM and DalvikVM

12. Why Scala

13. Java
public class MyActivity extends Activity {
ListView comments;
Button newComment;
@Override
void onCreate(Bundle bundle) {
super.onCreate(bundle);
comments = (ListView) findViewById(R.id.comments);
newComment = (Button) findViewById(R.id.new_comment);
//...
}
public void sayHello() {
Toast.makeText(this, “Hello”, Toast.LENGTH_LONG).show();
}
}
Initialize context and views

14. Java with RoboGuice
public class MyActivity extends RoboActivity {
@Inject Application context;
@Inject SessionManager sessionManager;
@Inject(R.id.comments) ListView comments;
@Inject(R.id.new_comment) Button newComment;
public void sayHello() {
Toast.makeText(this, “Hello”, Toast.LENGTH_LONG).show();
}
}
Inject views

15. GO HOME ANDROID. YOU ARE DRUNK.

16. Scala
class MyActivity extends ScalaActivity {
lazy val SessionManager
lazy val comments = findView(TR.comments)
lazy val newComment = findView(TR.new_comment)
def sayHello() = “Hello”.toast()
}
Lazily load views
Toast using implicit conversion
Implicit Context

17. A Sample Project

18. shadowsocks

19. shadowsocks
• github/shadowsocks/shadowsocks-android
• written in C/C++ and Scala
• modules
– shadowsocks-libev: secured socks5 proxy in pure C
– shadowsocks-android: UI/Android interface in Scala
– lwIP/tun2socks: user space TCP/IP stack in C++
– pdnsd/iptables/redsocks: native porting for android

20. Project Structure
project/
Build.scala <SBT makefile>
plugins.sbt <SBT plugin config>
src/
main/
res/ <resource files>
assets/ <asset files>
jni/ <native codes>
libs/ <jar and native libraries>
scala/ <main Scala sources>
java/ <main Java sources>
AndroidManifest.xml <manifest template>
test/ <test sources>

21. SBT
• Simple Build Tool for Scala / Java
– Ant, Maven, Gradle like tool in Scala
• github/jberkel/android-plugin
– SBT plugin for Android
– Dependency management, unit test, instrumentation, auto
tasks, etc

22. Components
• UI
– ActionBarSherlock
– SwitchBackport
– Crouton
– UnifiedPreference
– UniversalImageLoader
• Libraries
– DNSJava
– Analytics
– AdMob

23. Components

24. Best Practices
• Proguard
– Aggressive default rules
• IntelliJ IDEA
– Best IDE for Scala and Android
• Continuous Integration
– Travis is best, Jenkins works well

25. Questions?

26. Thanks!

27. About Me
• Max Lv
– Member of Tangcha Project
• 字节社 for Android, http://zijieshe.com
– Major Contributor of GoAgent Project
• github/madeye/gaeproxy
– Core maintainer of Shadowsocks Project
• github/madeye/shadowsocks-libev
• github/shadowsocks/shadowsocks-android